At present, this project is concentrating on investigating the modifiability of specific homeostatic processes that are basic to health. Although we have done some work on purely physiological mechanisms, such as enzyme induction, the main emphasis is on the role of learning -- both operant and classical conditioning -- in adjusting to new conditions or in producing maladjustments by shifting the priorities for the regulation of competing subsystems. For example, it is known that stimulation of the baroreceptors exerts an inhibitory effect on the reticular formation. We are investigating whether this inhibitory effect reduces the aversiveness of noxious stimulation, an effect that might be adaptive in life-threatening, fight-or-flight conditions. The effect on aversiveness will be investigated in a series of experiments comparing normal rats with those whose carotid sinus has been denervated and fibers from the aortic arch interrupted. It also will be investigated in pecise psychophysical studies of perception of mild pain. The next step will be to see whether such reduction in aversiveness can reinforce a simple instrumental response, and the final step will be to see whether it can reinforce an elevation in blood pressure analogous to some forms of essential hypertension. Other experiments will determine the degree to which changes in blood pressure to unusual manipulations of blood flow and unusual vasomotor responses to abnormal conditions of temperature can be learned. Finally, we plan to continue investigating the conditions producing optimum visceral learning in paralyzed rats and to develop this immobile but conditionable preparation further for its general utility in experiments requiring sophisticated neurophysiological techniques such as single-cell recording.